Self-aligning powdered metal bearing



Feb. 16, 1954 J. HALLER SELF-ALIGNING POWDERED METAL BEARING ZSZ S- Filed Feb. 15, 1950 Gttornegs Patented Feb. 16, 1954 UNITED :STATES PATENT Aoi-fr1cs SELF-ALIGNING POWDERED `METAL BEARING :lohn Haller, Northville, Mich., assigner 4to' Michigan lowdered .Metal Products -C0.,Inc., Northl fville, Mich., ,a corporation `of Michigan Application February 15, 1950,Seria1No.`144;3f13

(ci. .30sazi firmly against the inner bearing sleeveor elementbut wherein, `during sintering, a suitable clearance is set up therebetween, this clearance being of an accurately predetermined amount.

ln the drawings:

Figure 1 is a side elevation, partly in central vertical section, of a selt-aligning powdered metal bearing, according to the present invention;

Figure 2 is a front elevation, partly in section, of the bearing shown in Figure 1;

Figure 3 is a central `vertical section through the die cavity or mold of a molding press showing the start of the process oi molding the outer ring' or shell around the central bearing sleeve `or element;

Figure l is a View similar to Figure 3, but show'- ing the position of the `parts'at the `end of the molding operation;

Figure 5 is a side elevation, partly in section, of a self-aligning powdered metal pillow `block bearing produced according to the process of Figures 3 and fl;

6 is a iront elevation, partly in section, of the pillow block bearing shown in Figure 5;

Figure *I is a central vertical section through a molded self-aligning powdered metal bearing produced according to a modification of the process of the present invention, prior to sintering;

Figure y8 isa View similar to Figure 7 but show ing the bearing after sintering; and

Figure 9 is a central vertical section through a selnaliening powdered metal bearing produced by a further modication of the process of Figures 3 and l.

Referring to the drawings in detail, Figures 1 and 2 show a self-aligning powdered Ametal bearing, generally designated I (i, according to one form `of the invention and produced by one process according to the invention. The selfaligning bearing lil consists of a central `bearing sleeve or element II encircled by an outer bearing ring or shell I2, the members I I and I2 `being tiltable relatively to :one another to automatically align thevshaft which the bearing `I'0 rotatably ,2f supports.y The :bearing elementulfi is of annular form with a central bore lI3 fand an outer spherical surface I4 having its` center 'aia-the point IiS located on the axis .of the borrel-It. An 4internal annular oil `well I6: is preferablynpro-vided :in lthe wal-l of the bearing element 1I t. The bearingele ment II is disclosed and claimed .inmy `co-pend` ing `application Serial No. 81,274, .led March 14,

i949, "now Patent 2,625,452,` datedxdanuary 1,'3, 1&52, for -Porous Bearing With `Lubricant Rasera Voir Therein, while the process of making itl/s disclosedand claimed.v in my f-coepending application Serial No. 70,056, iiled January 10., 1949, for Powdered Metal Article :and :Process of Making the Same.

The outer shell or :ring I2 is provided with an` internal toroidalfcavity Il surrounding the spher ical `surface I4 and spaced away from it by a suitable clearance` to permit free :relative rocking motion Abetween the :element iII and ring l2. The `ring I2 has :an outer `surface I8, such :as a` cylindrical surface,` which is adapted to `be :secured in a suitable :bore orwsocket :in the machine in which the bea-ring is vto vbe used.`

In making the bearing HI shown `in Figures 1 and 2, `a suitable molding press, generally fdesignated 20 is provided, such as the molding press shown in my Vco-pending ramnlication SerialNo.

780,851, filed October 20,V ,1947,` `new Paten-t 2,668,826, dated Sept. 2, `1952, for Briquet-ting Machine, `but any other suitable molding press may be used. This presswthewdetals of [construction of which Aare beyond `:the fscopeof the 4presentinvention, includes upper and lower tubular orouter plungers 2| and 22 reciprocating into and .out of a bore or die cavity 23 in a die or mold :block 24 mounted on the bed of the press, The tubular plungers 2l and 22 Yare .in turn provided with central bores 25 and 2,5 respectively :in which upper and lower central for Ainner plungers 2-1 and 2,8` reciprocate, independently of ,and relatively to the upper and ylower outer yor tubular plungers 2-I and 22. In order to facilitate holdingand lining up the central. 4bearing elementtortsleeve .I.I, the upper and lower inner plungers `2l and .23 Aare optionally provided with reduced diameter pilot portions 29 and 3u surrounded by .annular shoulders SII and `32 respectively adapted toengage the opposite .ends of thebear-ing element II while the pilot portions 29 and 30 `enter the bore `I3 thereof. The upper and lower outer andiiinner plungers 2l, 22 ,and 21;, 2B are reciprocated in zany suitable manner, such was by ,.'hydraulicwmotors shown in `detail :inthe ahorre-mentioned suspend, ing application Ser..No.\Z8D;851. y

In the process of producing the self-aligning powdered metal bearing of Figures 1 and 2 I a :finished central bearing element or sleeve bearmg I I is selected, as disclosed in my above-mentioned co-pending applications. This bearing element 1s composed of powdered metal, such as powdered iron, containing a small percentage of copper, ior example 6 to 7 per cent, and having pores 1nltrated with an alloy of suitable composition, such as 85% copper and 15% zinc. This alloy, prior to sintering, was in the form of a ring of the size of the annular oil well or chamber I6 and filling that space. This core was produced in a press similar to the molding press 20 of Figures 3 and 4 by being placed in the die cavity, surrounded by powdered metal such as powdered iron which is thereupon compressed to a suitable density. This assembly is then sintered at a temperature of approximately 2020 F. for approximately one-half hour, during which the core melts and inltrates into the pores of the bearing element II, leaving the annular oil well or chamber I6 behind it. At the same time, the infiltration of the alloy into the side walls of the bearing increases the density of the bearing, improves its wearing qualities, and raises the temperature at which the alloy, or the copper constituent thereof, will emerge from the bearing. This increased temperature effect facilitates the carrying out of the process of the present invention.

The finished bearing sleeve or element II is placed in the die cavity 23 (Figure 3) upon the annular shoulder 32 of the lower inner plunger 28 which has been raised to a suitable height or level within the die cavity 23. The top surface 33 of the lower outer plunger 22 is also brought up to the desired level for the start of molding operations, which, as shown in Figure 3, is preferably a short distance below the level of the top surface 32 of the inner plunger 28. The reduced diameter pilot portion 30 of the lower inner plunger is caused to enter the bearing bore I3, thereby securely positioning the bearing element I I and preventing it from slipping. The upper inner plunger 2l is then lowered upon the top of the bearing element II (Figure 3) with its pilot portion 29 entering the bore I3 and its bottom surface 3l engaging the top surface of the bearing element I I. The plungers 2l and 28 are selected to be of such diameters that they completely occupy the upper and lower surfaces of the bearing element II, leaving only the spherical side surface I4 exposed.

The portion of the die cavity around the bearing element II is then lled with the powdered metal of which the outer ring I2 is to be composed, for example, powdered iron containing 6 to 7 per cent copper. An expanding metal powder, known as a so-called growing powder which expands during sintering, is used for the ring I2 as distinguished from powders which shrink or contract during sintering. Such growing powders are known to the powder metallurgy art and given in standard texts thereon. When the die cavity 23 has been lled to the desired height, the upper outer tubular plunger 2i is moved downward and the lower outer tubular plunger 22 is moved upward until their end surfacesvS and 33 arrive approximately opposite and on the same level with the surfaces 3I and 32 of the inner plungers 2l and 28 (Figure 2). The powdered metal filling the die cavity 23 is thus compressed into an annular space surrounding the nished central bearing element il.

then forms an annular mass 35 of unsintered growing powder of powdered metal.

The outer and inner upper plungers 2| and 2`I are now retracted upward out of the die cavity or bore 23 and the lower outer and inner plungers 22 and 23 are advanced upward to expel the semi-nished or unsintered bearing, generally designated 26, from the die cavity 23.

The semi-nished bearing 33 is now placed in a sintering oven and the temperature raised to about 1900D F. and sintered at this temperature for approximately one-half hour. Care is taken to avoid raising the sintering temperature to an excessively high degree, in order to prevent the ow of the copper out of the central bearing element II, this copper being impregnated therein during the previous sintering and inltration. As previously stated, the copper which has iniiltrated the central bearing element Il in its iirst sintering will flow out during a subsequent sintering only at a heightened temperature, so that the danger of an outflow of copper from the central bearing element il can be easily avoided by carefully controlling the temperature at which the second sintering or sintering of the outer ring powder 35 is carried out.

During the sintering operation, the powdered metal ring portion 35 expands outward more than the central bearing element II due to the fact that the outer portion 315 is of a growing powder, resulting in the formation of an annular gap or clearance 3l (Figure 1) between the opposed spherical surfaces Ili and VI on the outside of the central bearing element Ii and inside of the bearing ring or outer shell i2 respectively. For this reason, the former will rock freely and easily relatively to the latter, thereby bringing about the self-aligning action of the bearing I0.

n the event that the bearing element or sleeve Ii and ring or outer shell I2 are made of powdered bronze instead of powdered iron, the procedure is similar except that a lower sintering temperature must be used since powdered bronze bearings are sintering at approximately 1500 F. The length of time for sintering either bearing depends, of course, upon the size of the bearing, the previously-mentioned time of one-half hour being suitable for a small bearing.

The pillow block self-aligning powdered metal bearing liii shown in Figures and b is produced by the same process as the annular bearing ID shown in Figures l to fi inc. except that the die cavity 23 has a cross-section corresponding to the outline of the outer or pillow block portion 4i, this being ollset relatively to the axis of the bearing because cf the base portion d2 which is likewise oiset. The central portion or bearing element 43 is produced in the saine manner as the bearing element li previously described and is manipulated in the same way in the molding press 2t. The upper and lower outer plungers 2l and 22 are, of course, made with cross sections corresponding to the outline of the pillow block portion ffii, the same as the die cavity 23. The process is otherwise substantially the same and hence requires no repetition. The pillow block bearing il?! is, of course, used in locations where it is to be mounted upon a fiat surface by the use of its base portion i132 rather-than inserted in a bore.

The modied powdered metal bearing 50 of Figure 3 is made in a closely similar manner to the bearing Iii of Figures l and and the procedure within the molding press 23 is identical.

Prior to inserting the central bearing element Il.

in the press, however, it is provided with a coating 5| of a metal or alloy which is iniiltratable during sintering into the material of the outer ring portion 52. It will not inltrate to any great extent into the inner bearing element 53 because this has already been sintered once and accordingly has much less tendency to absorb additional metal. The layer 5| may be deposited by plating or spraying and may consist of the same inltratable alloy of 85% copper and 15% zinc previously mentioned, assuming that the unsintered outer portion 52 is of powdered iron. The thickness of the layer 5| is determined by the clearance 54 which it is desired to have between the outer and inner bearing portions 52 and 53 (Figure 8).

The inner bearing element 53, coated with the infiltratable metal layer 5|, is placed in the molding press 2D, as before (Figure 3) and the die cavity 23 filled with powdered iron or other suitable powdered metal particles. Due to the presence of the layer or coating 54, however, it is unnecessary to use a growing powder as before. When the mold charge has -been compressed (Figure 4), the article is withdrawn from the press 2U as before and placed in a sintering oven for the second sintering operation. This is car ried out, as before, at a temperature sufficiently high to cause the layer metal 5| to inltrate the pores of the outer shell 52 without setting up an outflow of metal from the pores of the inner bearing element or sleeve 53. The disappearance of the layer metal 5| in this manner during sintering leaves the desired clearance space 54 between the outer and inner bearing members 52 and 53 (Figure 8) and enables free selfaligning rocking motion to occur. The sintering operation, of course, hardens the outer shell or ring 52 at the same time the layer metal 5| is being infiltrated therein. A sintering temperature of approximately 1900 F. for approximately one-half hour is found suitable for a small bearing.

The process of making the powdered metal self-aligning bearing 60 shown in Figure 9 follows a similar procedure as that previously described in connection with Figures 1 to 4 inc. In order to positively insure that no brazing or alloying between the outer and inner bearing elements 6| and 52 can occur during sintering, a layer 63 of a suitable anti-alloying material such as graphite or a graphitic composition is placed upon the outer surface of the inner bearing element or sleeve 62. An expanding or growing powder is preferably used in order to insure an adequate clearance between the elements 6| and 62. During sintering, which is carried out at approximately the same temperature and for approximately the same time periods as described above. the layer 63 prevents flow of copper between the inner bearing element 62 and the outer ring or shell 6|, even though the sintering temperature is raised to a higher degree than is employed in the process of Figures 1 to 4 inclusive. Thus, in producing the bearing 6|) of Figure 9, less care is needed in maintaining the maximum temperature of the second sintering at or below the critical temperature level which might otherwise cause an outflow of copper from the previously sintered inner bearing element or sleeve 62.

What I claim is:

1. A self-aligning powdered metal bearing comprising a one-piece inner bearing element of powdered metal having a bore therein and a spherical outer bearing surface therearound, and a one-piece outer bearing element of powdered metal having an internal spherical bearing surface therein receiving and encircling said outer surface of said inner bearing element with an annular clearance space therebetween, said outer bearing element being formed of powdered metal of growing powder characteristics.

2. A self-aligning powdered metal bearing comprising a one-piece inner bearing element of powdered metal having a bore therein and a spherical outer bearing surface therearound, and a one-piece outer bearing element of powdered metal having an internal spherical bearing surface therein receiving and encircling said outer surface of said inner bearing element with an annular clearance space therebetween, the adjacent surfaces of said bearing elements within said clearance space being impregnated with a metal dissimilar to the metal of said bearing elements.

3. A self-aligning powdered metal. bearing comprising an inner bearing element of powdered metal having a bearing bore therein and a spherical outer surface therearound, and a onepiece outer bearing element of powdered metal having an internal spherical surface therein receiving and encircling said outer surface of said inner bearing element with an annular clearance space therebetween, one of said bearing elements having a layer of anti-alloying material thereon within said clearance space.

4. A self-aligning powdered metal bearing comprising an inner bearing element or powdered metal having a bearing bore therein and a spherical outer surface therearound, and a onepiece outer bearing element of powdered metal having an internal spherical surface therein receiving and encircling said outer surface of said inner bearing element with an annular clearance space therebetween, one of said bearing elements having a layer of graphitic material thereon within said clearance space.

JOHN HALLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,664,189 Claus i Mar. 27, 1928 1,896,939 Calkins Feb. 7, 1933 1,903,483 Skillman Apr. 11, 1933 2,441,294 Shafer May 11, 1948 2,461,765 Olt Feb. 15, 1949 

